Field of the Invention
The present invention relates to a device and a method for measuring the capacitance of a dielectric elastomer, which elastically deforms according to an applied voltage.
Description of the Related Art
A dielectric elastomer has the property that, when a voltage is applied thereto, the dielectric elastomer is compressed by Maxwell stresses in the direction of an electric field attributable to the applied voltage. Further, the stiffness or the like of the dielectric elastomer can be controlled to a required target state by variably manipulating the voltage applied to the dielectric elastomer (hereinafter may be referred to simply as “the elastomer”). For this reason, the elastomer has been used in a variety of technical fields in recent years (refer to, for example, Japanese Patent Application Laid-Open No. 2003-174205).
In the case where the voltage applied to an elastomer is variably manipulated in order to control the stiffness or the like of the elastomer to a required target state, it is frequently desired that a state amount closely related to an actual elastic deformation state of the elastomer can be acquired in order to properly perform the control.
In this case, for example, the amount of the elastic deformation of the elastomer may be directly measured using a displacement sensor, such as a distance sensor or the like. However, the displacement sensor must be placed in the vicinity of the elastomer, frequently leading to structural restrictions thereto. Further, the elastomer is flexible and may develop shape deformation in response to an external force, making it generally difficult to measure the amount of the elastic deformation of the elastomer with high reliability by using a displacement sensor.
Meanwhile, the elastomer is an electrical insulator and therefore functions as a capacitive element. The capacitance of the elastomer as a capacitive element has a high correlation with the thickness (the thickness in the direction in which an electric field acts) or the shape dimensional values, such as area, of the elastomer. Further, the capacitance of the elastomer can be estimated from a detected electrical value, such as a current value or the like, so that a system for measuring the capacitance has minimal structural restrictions.
Hence, the capacitance of the elastomer may be measured as the state amount closely related to the actual elastic deformation state of the elastomer. In this case, it is desired that the capacitance of the elastomer can be measured with high reliability while allowing the voltage applied to the elastomer to be variably manipulated.